What else could cause the tummy aches?
She changes the frequency of her feeds quite regularly, sometimes I worry I'm not giving her enough because she'll feed, then play for an hour and a half then sleep for two hours.

..I really have no idea what I'm doing here.
What about this are you worried about? It sounds fine to me.

Although we don't always know what's going on, babies usually do. A 5 hour sleep stretch at 3 months is really good.